Interconnect structures are used in semiconductor manufacturing to connect active and passive devices or structures at different wiring levels of the chip. Interconnect structures can be composed of different metal or metal alloy materials such as, e.g., tungsten (W) or copper (Cu). For example, middle of the line processes typically include tungsten; whereas, back end of the line processes typically include copper.
By virtue of continued scaling of device technologies, interconnect structures need to be reduced in size. For example, interconnect structures with dimensions of less than 20 nm are now required in many semiconductor processes. As the interconnect structures scale downwards, different metals or metal alloys are required with lower resistivities in order to improve device performance.